Shuttle Panel Keys On Joint Seals, Cold

WASHINGTON — The presidential commission investigating the space shuttle Challenger explosion focused Tuesday on the effects of cold weather on seals connecting segments of the shuttle`s booster rockets, including special putty and rubber rings used in the joints.

Internal space agency memos released by the commission identified the putty used in field joints on the rocket segments as the ``prime suspect``

contributing to erosion discovered in the ``O rings,`` 12-foot-long sections of rubber placed at booster joints to prevent the escape of hot gases from the solid fuel.

In a second day of public hearings, the commission heard testimony from officials of the National Aeronautics and Space Administration about NASA studies that had indicated there were problems with those materials long before the Jan. 28 crash killed Challenger`s crew of seven.

Despite the focus of Tuesday`s hearings, it was apparent from testimony that the commission has not yet reached a conclusion as to the exact cause of the disaster or what role seal and joint problems may have played in the shuttle disaster.

Meanwhile, in Cape Canaveral, Fla., a Kennedy Space Center official said Tuesday that Challenger`s booster rockets were never inspected for possible defects from cold weather or other risk factors during the 38 days that the shuttle sat on a launch pad awaiting liftoff.

Despite problems with booster parts on previous shuttle flights and warnings that cold weather could have potentially disastrous effects, NASA technicians did not subject the boosters to structural scrutiny at any point during the pre-launch period, said Thomas Utsman, deputy director of the space center.

NASA inspectors do not check at the launch site for any booster problems that may develop during transportation of the shuttle from an assembly building about four miles away, according to Utsman.

Once the shuttle moves to the pad, Utsman said, ``essentially it is considered a structurally stable vehicle. There is no final check as far as structural integrity at that point.``

In Washington, the presidential commission released a memo by NASA budget analyst Richard Cook written six days after the shuttle disaster. In it, Cook wrote that NASA engineers believed that if there was a burn-through in the casing on the right booster, as officials now believe, ``it was probably preventable and that for well over a year, the solid rocket boosters have been flying in an unsafe condition.``

Cook attributed this to ``the problem of O-ring erosion.``

Cook wrote the Feb. 3 memo to his boss, Michael Mann, chief of the shuttle resource analysis branch in the office of the NASA comptroller. Cook concluded that whether the O-ring problem caused the disaster or not, it

``must be repaired before the shuttle can fly again.`` He said problems with the solid rocket boosters could suspend shuttle flights for ``a minimum of nine months and possibly as long as two years or more.``

Cook said NASA planners recently have been in the ``very difficult situation`` of making program judgments at a time when funding was getting scarce. ``The budget was coming down very steeply while at the same time the flight schedule was going up.``

Cook drew attention to the putty that is used to cover the interior gap in the field joints segment, enclosing two O-rings known as the primary and secondary seal. ``It is clear that the field joint putty plays a significant role in O-ring erosion,`` Cook concluded.

In an earlier memo, dated July 23, 1985, also intended for Mann, Cook wrote: ``There is little question . . . that flight safety has been and is still being compromised by potential failure of the seals, and it is acknowledged that failure during launch would certainly be catastrophic.``

That memo was also released by the commission on Tuesday.

Another memo released Tuesday was written in June, 1985, by Irving Davids, a Washington-based solid rocket booster engineer for NASA, to Jesse Moore, associate administrator of space flight. Davids wote that a putty used on all shuttle missions since the 10th one is the ``prime suspect as the cause for the erosion on the primary O-ring seals.``

He also said that the putty ``is believed to be more susceptible to environmental effects such as moisture, which makes the putty more tacky.``

And Lawrence Mulloy, solid rocket booster project manager at the Marshall Space Flight Center in Huntsville, Ala., testified that a ``flaw in the putty could cause a hot gas jet to intrude`` into a gap between field joints and

``then a hot gas jet could erode an O-ring.``

Moore, Mann and senior NASA officials testified Tuesday that Cook was exaggerating the concerns of engineers here and stated that agency analysts deemed the boosters to be safe and flightworthy before Challenger was allowed to blast off.